Ray Tomlinson

Raymond Samuel Tomlinson was an American computer programmer who invented the first email program on the ARPANET system, the precursor to the Internet, in 1971; it was the first system able to send mail between users on different hosts connected to ARPANET. Previously, mail could be sent only to others who used the same computer. To achieve this, he used the @ sign to separate the username from the name of their machine, a scheme which has been used in email addresses ever since.